This application proposes studies in a variety of areas relating to the chemistry and biology of human lymphocytes. The problems being studied involve the molecular basis of immune recognition as well as factors which govern and regulate proliferation of human lymphocytes. The techniques being employed include protein chemistry and crystallography, molecular genetics, immunology and virology. Specific areas of investigation are 1) protein chemistry and crystallography of immune recognition molecules, 2) relationship of structure to function in class I and class II MHC molecules, 3) cloning the human major histocompatibility complex, especially the location of tumor necrosis factor genes within it, 4) expression of human class II antigens, 5) regulation of transcription of human class II MHC genes, 6) studies of T cell receptors particularly the role of the TCR gamma delta receptor in immunosurveillance, 7) the Epstein-Barr Virus particularly the nature of the viral functions which induce cell proliferations, 8) the role of the 4F2 protein in cell proliferation.